High-performance Fe-doped ZIF-8 adsorbent for capturing tetracycline from aqueous solution

Nanozyme-based colorimetric and smartphone imaging advanced sensing platforms for tetracycline detection and removal in food

The presence of antibiotic residues poses a significant threat to food assurance, triggering widespread concerns. Therefore, the prompt and accurate detection and removal of antibiotic residues are essential for ensuring food safety. In this study, an aptmer modified triple-metal nanozyme (apt-TMNzyme) sensor was developed, which achieved a portable, visual, intelligent, and fast determination for tetracycline (TET). The proposed apt-TMNzyme exhibited willow leaf-like morphology, high specific surface area and excellent TET adsorption and removal properties. The experiments showed that the apt-TMNzyme had outstanding peroxidase activity and could catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce a blue product in the presence of H2O2, which provided a visual response signal to TET. This sensor was capable of quantifying TET within a concentration range of 0.2 nM-70 μM, achieving a detection limit of 7.1 nM under optimal conditions. When tested on real food samples, our sensor produced results that closely paralleled those achieved through high-performance liquid chromatography. To improve accessibility and user-friendliness, we also designed a colorimetric testing paper integrated with a smartphone application for intuitive and intelligent detection of TET, which enables the quantitative determination of TET in the concentration range of 0.003-60 μM, the detection limit was 5.1 μM. This integrated portable sensor not only streamlines the testing process, saving time and costs, but also offers a promising solution for rapid and sensitive detection of antibiotic residues.

A LMOF/MIP paper-based chip and analysis of tetracycline in foodstuff with sample-to-answer performance

The development of high-performance specific sensors is promising for the rapid detection of harmful residues in animal-derived foods. Recently, luminescent metal-organic framework/molecularly imprinted polymer (LMOF/MIP) materials have been developed as ideal candidates for the analysis of harmful residues. Here, we reported a simple fabrication protocol of paper-based chip through in-situ growth of LMOF on a negatively charged modified filter paper, a paper-based molecularly imprinting layer (FP@BA-Eu@MIP) was thereafter successfully prepared via the boronate affinity-based controllable oriented surface imprinting strategy. The paper-based chips obtained were used to construct a rapid test strip of tetracycline (TC). After addition of TC, significant fluorescence changes on the surface of the FP@BA-Eu@MIP paper-based chip could be observed from blue to red via inner filter effect and photo-induced electron transfer under the excitation of 360 nm. The adsorption kinetics was explored in detail. The presented strip exhibited satisfied selectiveness and sensitivity with a limit of detection of 8.47 μg L-1 for TC. It was confirmed that LMOF/MIP as a biomimetic recognition module can play a crucial role in enrichment and fluorescence response. This study provided a real application case for an in-situ fabricated fluorescence paper-based chip in rapidly detecting harmful residues.

Polysaccharide-based biopolymeric magnetic hydrogels for remediation of antibiotics from aqueous solution

Polysaccharide-based biopolymeric magnetic hydrogels have garnered significant attention as effective materials for wastewater treatment due to their high adsorption capacity and environmentally friendly nature. This review examines recent advancements in the development of biopolymeric magnetic hydrogels derived from polysaccharides such as cellulose, chitosan, alginate, carrageenan, starch, and gums, with a focus on their application in removing antibiotics from contaminated water as it not only enhances adsorption performance but also simplifies separation processes after treatment, making them highly efficient for practical applications. The review aims to provide a comprehensive overview of the synthesis techniques, performance characteristics, and interaction mechanisms of these hydrogels, highlighting their renewability and suitability for large-scale water treatment. Despite their promise, there is a lack of in-depth analysis of their performance and fabrication methods. This review addresses this gap by evaluating various synthesis methods and assessing the hydrogels' efficiency in adsorbing antibiotic pollutants. Key findings reveal that the biopolymeric and magnetic components contribute to the materials' enhanced binding, better removal capabilities, and easy recoverability. The interaction mechanisms between the hydrogels and antibiotics are explored, demonstrating their superior adsorption potential. Future challenges and research directions are discussed, with an emphasis on improving the scalability and practical applications of these hydrogels. Overall, this review offers valuable insights into the development and potential of biopolymeric magnetic hydrogels to contribute towards effective wastewater purification.

Plasma-induced Fe-doped zeolitic imidazolate framework-8 derived P-Fe-N3C for enhanced phenol degradation

Plasma-synergistic catalysis is considered an effective method for degrading aromatic organic pollutants in water. However, the underlying synergistic catalytic mechanism between plasma and catalysts remains poorly understood. Here, we propose a plasma-metal organic frameworks (MOFs) synergistic strategy to investigate the mechanism of plasma-synergistic catalysts for phenol degradation. The results show that Fe-doped Zeolitic Imidazolate Framework-8 (Fex-ZIF8, x = 0, 0.1, 0.2, 0.4) undergoes the plasma-induced transformation into an Fe-N3C structure (P-Fe-N3C), leading to a 4.5-fold enhancement in the phenol degradation rate compared to only plasma discharge. Density functional theory (DFT) calculations indicate that the plasma-induced structural transformation of Fex-ZIF8 promotes the redistribution of point charges and space charges around the Fe center, thereby lowering the activation energy barrier in the rate-determining step (*C6H4(OH)2). These findings not only provide theoretical support for the degradation of water pollutants via plasma-synergistic catalysts but also offer a novel strategy for constructing MOFs-derived materials.

Photothermally Reinforced Nanozyme Remodeling Tumor Microenvironment of Redox and Metabolic Homeostasis to Enhance Ferroptosis in Tumor Therapy

The acidity and high GSH level in the tumor microenvironment (TME) greatly limit the antitumor activity of nanozymes. Thus, enhancing nanozymes' activity is fundamentally challenging in tumor therapy. Although the combination of photothermal therapy (PTT) and nanozymes can enhance the catalytic activity, cancer cells will overexpress heat shock proteins (HSPs) at high temperature, aggravating the heat resistance of tumor cells, which in turn compromises the outcome of chemodynamic therapy. Herein, we propose an iron-doped metal-organic framework nanozyme (IB@Fe-ZIF8@PDFA) that can be activated under the weak acidity and high level of GSH, demonstrating the activities of GSH oxidation (GSH-OXD), peroxidase (POD), and NADH oxidase (NADH-OXD). Under laser irradiation, it displays photothermal-enhanced multienzyme activities to simultaneously eliminate tumors and inhibit tumor metastasis. While consuming endogenous GSH, IB@Fe-ZIF8@PDFA promotes the decomposition of H2O2 into ·OH, enhancing ferroptosis in tumor cells. Surprisingly, IB@Fe-ZIF8@PDFA nanozyme can oxide NADH and subsequently limit the ATP supply, reducing the expression of HSPs and significantly weakening the heat resistance of tumor cells during PTT. Meanwhile, H2O2 is generated during this procedure, which can endogenously replenish the consumed H2O2. Thus, this IB@Fe-ZIF8@PDFA nanozyme constitutes a self-cascading platform to consume GSH and NADH, endogenously replenish the H2O2 and continuously generate ·OH to facilitate ferroptosis by disrupting the redox and metabolic homeostasis in tumor cells, achieving tumor elimination and tumor metastasis inhibition.

Zeolites in wastewater treatment: A comprehensive review on scientometric analysis, adsorption mechanisms, and future prospects

Zeolites possess a microporous crystalline structure, a large surface area, and a uniform pore size. Natural or synthetic zeolites are commonly utilized for adsorbing organic and inorganic compounds from wastewater because of their unique physicochemical properties and cost-effectiveness. The present review work comprehensively revealed the application of zeolites in removing a diverse range of wastewater contaminates, such as dyes, heavy metal ions, and phenolic compounds, within the framework of contemporary research. The present review work offers a summary of the existing literature about the chemical composition of zeolites and their synthesis by different methods. Subsequently, the article provides a wide range of factors to examine the adsorption mechanisms of both inorganic and organic pollutants using natural zeolites and modified zeolites. This review explores the different mechanisms through which zeolites effectively eliminate pollutants from aquatic matrices. Additionally, this review explores that the Langmuir and pseudo-second-order models are the predominant models used in investigating isothermal and kinetic adsorption and also evaluates the research gap on zeolite through scientometric analysis. The prospective efficacy of zeolite materials in future wastewater treatment may be assessed by a comparative analysis of their capacity to adsorb toxic inorganic and organic contaminates from wastewater, with other adsorbents.

Construction of carbon-doped iron-based nanozyme for efficient adsorption and degradation to synergistic removal of aflatoxin B1

The multifunctional composites Fe3O4/GO/NH2-MIL-53(Fe) with excellent adsorption-degradation performance was prepared for the removal of Aflatoxin B1 (AFB1). The adsorption function of Fe3O4/GO/NH2-MIL-53(Fe) was based on the large specific surface area and abundant adsorption sites. The degradation function of Fe3O4/GO/NH2-MIL-53(Fe) was based on the activation of H2O2 by the catalytic active center formed by the coordination of metal ions and oxygen-containing groups in the system, resulting in hydroxyl radicals (·OH), superoxide anion radicals (O2-) and singlet oxygen (1O2). The adsorption of nanozyme accelerated the degradation reaction process, and the adsorption site was further exposed as the degradation process progressed. The synergistic effect realized the efficient removal of AFB1. Construction of Fe3O4/GO/NH2-MIL-53(Fe) as the carbon-doped iron-based nanozyme provided novel approaches of the removal for risks control of AFB1. Accompanied by the AFB1 adsorption, the advanced oxidation of nanozyme to the AFB1 degradation provided a promising way for the synergistic removal of AFB1.

Deep learning assisted logic gates for real-time identification of natural tetracycline antibiotics

The overuse and misuse of tetracycline (TCs) antibiotics, including tetracycline (TTC), oxytetracycline (OTC), doxycycline (DC), and chlortetracycline (CTC), pose a serious threat to human health. However, current rapid sensing platforms for tetracyclines can only quantify the total amount of TCs mixture, lacking real-time identification of individual components. To address this challenge, we integrated a deep learning strategy with fluorescence and colorimetry-based multi-mode logic gates in our self-designed smartphone-integrated toolbox for the real-time identification of natural TCs. Our ratiometric fluorescent probe (CD-Au NCs@ZIF-8) encapsulated carbon dots and Au NCs in ZIF-8 to prevent false negative or positive results. Additionally, our independently developed WeChat app enabled linear quantification of the four natural TCs using the fluorescence channels. The colorimetric channels were also utilized as outputs of logic gates to achieve real-time identification of the four individual natural tetracyclines. We anticipate this strategy could provide a new perspective for effective control of antibiotics.

Surface coordination induced a quasi p-n junction for efficient visible light driven degradation of tetracycline over hydroxyapatite

The removal of antibiotics from aquatic solutions remains a global environmental challenge. In this work, the photocatalytic removal of a typical antibiotic-tetracycline (TC) using hydroxyapatite (HAp) as a catalyst was investigated. It was impressive that TC could be efficiently degraded by HAp under visible light irradiation, even though both HAp and TC exhibited poor harvesting in visible light region. The experimental and theoretical explorations were undertaken to thoroughly investigate the underlying mechanism of visible light degradation of TC over HAp. The results indicated that the formed TC-HAp complexes via surface coordination played an important role as photosensitizers for the visible light response. Together with the formation of a quasi p-n junction via band alignment, the photogenerated electrons in the highest unoccupied molecular orbital (HOMO) of TC-HAp were excited to the lowest unoccupied molecular orbital (LUMO) and subsequently migrated to the conduction band of HAp to achieve the efficient charge separation. Superoxide radicals and holes were found to be the major active species for TC degradation. The toxicity evaluation showed that TC could be transferred to the lower toxic intermediates, and deep oxidation with prolonged reaction time was necessary to eliminate the toxicity of TC. This work demonstrates the surface coordination with subsequent quasi p-n junction mechanism of TC degradation over HAp under visible light, which will stimulate us to explore new efficient photocatalytic systems for the degradation of various contaminants.

Synthesis of Nanosized γ-Cyclodextrin Metal-Organic Frameworks as Carriers of Limonene for Fresh-Cut Fruit Preservation Based on Polycaprolactone Nanofibers

To address the issue of bacterial growth on fresh-cut fruits, this paper reports the synthesis of nanosized γ-cyclodextrin metal-organic frameworks (CD-MOFs) using an ultrasound-assisted method and their application as carriers of limonene for antibacterial active packaging. The effects of the processing parameters on the morphology and crystallinity of the CD-MOFs are investigated, and the results prove that the addition of methanol is the key to producing nanosized CD-MOFs. The limonene loading content of the nanosized CD-MOFs can reach approximately 170 mg g-1. The sustained-release behaviors of limonene in the CD-MOFs are evaluated. Molecular docking simulations reveal the distribution and binding sites of limonene in the CD-MOFs. CD-MOFs are deposited on the surfaces of polycaprolactone (PCL) nanofibers via an immersion method, and limonene-loaded CD-MOF@PCL nanofibers are prepared. The morphology, crystallinity, thermal stability, mechanical properties, and antibacterial activity of the nanofibers are also studied. The nanofiber film effectively inhibits bacterial growth and prolongs the shelf life of fresh-cut apples. This study provides a novel strategy for developing antibacterial active packaging materials based on CD-MOFs and PCL nanofibers.

Zeolitic imidazolate framework derived Fe catalyst electrocatalytic-driven atomic hydrogen for efficient reduction of nitrate to N2

Excessive discharge of nitrogen-containing chemical products into the natural water environment leads to the serious environmental problem of nitrate-nitrogen pollution, threatening the ecological balance and human health. In this study, we propose an efficient denitrification electrochemical method utilizing iron-doped zeolite imidazolium framework derived defective nitrogen-doped carbon (d-FeNC) catalysts. The d-FeNC catalyst exhibited 97 % nitrate removal efficiency and 94 % total nitrogen (TN) removal, and the reaction rate constant was increased from 0.73 h-1 of the Fe-undoped electrocatalyst (d-NC) to 1.11 h-1. The successful synthesis of d-FeNC with carbon defect sites and encapsulated Fe was confirmed by in-depth characterization. In situ electron paramagnetic resonance (EPR) analysis in conjunction with cyclic voltammetry (CV) tests confirmed the carbon substrates with defect enhanced the trapping of atomic hydrogen (H*) on the catalyst surface. Density functional theory (DFT) calculations clarified the doping of Fe facilitated the adsorption of nitrate, resulting in contact of H* with nitrate on the catalyst surface. In the synergy of the defective state organic framework and metal Fe, H* and nitrate realized a collision process. The electrochemical denitrification system achieved an excellent nitrate removal capacity of 7587 mgN·g-1cat in high-concentration nitrate solution and showed excellent stability under various conditions. Overall, this study underscores the potential of defective iron-doped carbon catalysts for efficient electrocatalytic denitrification, providing a promising approach for sustainable wastewater treatment.

Sensitive dual-signal detection and effective removal of tetracycline antibiotics in honey based on a hollow triple-metal organic framework nanozymes

In this work, a colorimetric/fluorescent dual-signal mode sensor is proposed for the sensitive, selective and accurate detection and removal of tetracycline antibiotics (TCs). A triple-metal MOF of NiCoFe is successfully synthesized and controllable adjusted the shape of the hollow structure for the first time, and then modified with TCs aptamer. The as-prepared triple-atom MOF (apt-NiCoFe-MOF-74) exhibits well-defined hollow morphology, high crystallinity, and high surface areas endow their alluring adsorption and removal performances for TCs. More attractively, this triple-metal MOF show a good peroxidase-like activity and strong fluorescence property at 540 nm of apt-NiCoFe-MOF-74 when excitation wavelength was 370 nm. Inspire by this, a dual-signal output biosensor is constructed and the linear absorbance response is well correlated with wide range and low LOD for TCs. The biosensor provided an universal method with satisfactory sensitivity and accuracy for TCs analysis in real food samples.

Enhanced sorption and fluorescent detection of bisphenol A by using sodium alginate/cellulose nanofibrils/ZIF-8 composite hydrogel

To address the issue of bisphenol A (BPA) contamination in wastewater, a novel hydrogel, sodium alginate/cellulose nanofibrils/ZIF-8 composite hydrogel (SCZC), was synthesized for efficient BPA removal. The SCZC exhibited an exceptional adsorption capacity of 1696 mg/g, aligning well with both Langmuir and pseudo-second-order models. Furthermore, it exhibited remarkable regeneration properties, maintaining 89.1 % of its adsorption capacity even after undergoing five adsorption-desorption cycles. The synthesized SCZC also acted as a fluorescent sensor for detecting BPA, employing dynamic quenching and offering linear detection ranges of 10-100 mg/L and 0.2-1.0 μg/L, with a low detection limit of 0.06 μg/L. Analysis of adsorption and detection mechanisms revealed that SCZC's exceptional performance could be attributed to the three-dimensional (3D) porous structure formed by sodium alginate and cellulose nanofibrils. Economic analysis indicated that SCZC, in comparison to commercially activated carbon, was relatively inexpensive. This study introduces a novel approach for designing and preparing a sodium alginate-based hydrogel incorporating metal-organic frameworks, offering simultaneous BPA detection and removal capabilities.

Multilayered Fe3O4@(ZIF-8)3 combined with a computer-vision-enhanced immunosensor for chloramphenicol enrichment and detection

The misuse and overuse of chloramphenicol poses severe threats to food safety and human health. In this work, we developed a magnetic solid-phase extraction (MSPE) pretreatment material coated with a multilayered metal-organic framework (MOF), Fe3O4 @ (ZIF-8)3, for the separation and enrichment of chloramphenicol from fish. Furthermore, we designed an artificial-intelligence-enhanced single microsphere immunosensor. The inherent ultra-high porosity of the MOF and the multilayer assembly strategy allowed for efficient chloramphenicol enrichment (4.51 mg/g within 20 min). Notably, Fe3O4 @ (ZIF-8)3 exhibits a 39.20% increase in adsorption capacity compared to Fe3O4 @ZIF-8. Leveraging the remarkable decoding abilities of artificial intelligence, we achieved the highly sensitive detection of chloramphenicol using a straightforward procedure without the need for specialized equipment, obtaining a notably low detection limit of 46.42 pM. Furthermore, the assay was successfully employed to detect chloramphenicol in fish samples with high accuracy. The developed immunosensor offers a robust point-of-care testing tool for safeguarding food safety and public health.

Dual-ROS-scavenging and dual-lingering nanozyme-based eye drops alleviate dry eye disease

Efficiently removing excess reactive oxygen species (ROS) generated by various factors on the ocular surface is a promising strategy for preventing the development of dry eye disease (DED). The currently available eye drops for DED treatment are palliative, short-lived and frequently administered due to the short precorneal residence time. Here, we developed nanozyme-based eye drops for DED by exploiting borate-mediated dynamic covalent complexation between n-FeZIF-8 nanozymes (n-Z(Fe)) and poly(vinyl alcohol) (PVA) to overcome these problems. The resultant formulation (PBnZ), which has dual-ROS scavenging abilities and prolonged corneal retention can effectively reduce oxidative stress, thereby providing an excellent preventive effect to alleviate DED. In vitro and in vivo experiments revealed that PBnZ could eliminate excess ROS through both its multienzyme-like activity and the ROS-scavenging activity of borate bonds. The positively charged nanozyme-based eye drops displayed a longer precorneal residence time due to physical adhesion and the dynamic borate bonds between phenyboronic acid and PVA or o-diol with mucin. The in vivo results showed that eye drops could effectively alleviate DED. These dual-function PBnZ nanozyme-based eye drops can provide insights into the development of novel treatment strategies for DED and other ROS-mediated inflammatory diseases and a rationale for the application of nanomaterials in clinical settings.

Fe, N, S co-doped carbon network derived from acetate-modified Fe-ZIF-8 for oxygen reduction reaction

In this work, potassium acetate (KAc) was added during the synthesis of a Zn-Fe based metal-organic framework (Fe-ZIF-8) to increase the fixed amount of Fe while simultaneously enhancing the number of pores. Electrospinning was utilized to embed KAc-modified Fe-ZIF-8 (Fe-ZIF-8-Ac) into the polyacrylonitrile nanofiber mesh, to obtain a network composite (Fe@NC-Ac) with hierarchical porous structure. Fe@NC-Ac was co-pyrolyzed with thiourea, resulting in Fe, N, S co-doped carbon electrocatalyst. The electrochemical tests indicated that the prepared catalyst displayed relatively remarkable oxygen reduction reaction (ORR) catalytic activity, with an onset potential (Eonset) of 1.08 V (vs. reversible hydrogen electrode, RHE) and a half-wave potential (E1/2) of 0.94 V, both higher than those of the commercial Pt/C (Eonset = 0.95 V and E1/2 = 0.84 V), respectively. Assembled into Zn-air batteries, the optimized catalyst exhibited higher open circuit voltage (1.698 V) and peak power density (90 mW cm-2) than those of the commercial 20 wt% Pt/C (1.402 V and 80 mW cm-2), respectively. This work provided a straightforward manufacturing strategy for the design of hierarchical porous carbon-based ORR catalysts with desirable performance.

Phosphorus removal from water by the metal-organic frameworks (MOFs)-based adsorbents: A review for structure, mechanism, and current progress

Efficacious phosphate removal is essential for mitigating eutrophication in aquatic ecosystems and complying with increasingly stringent phosphate emission regulations. Chemical adsorption, characterized by simplicity, prominent treatment efficiency, and convenient recovery, is extensively employed for profound phosphorus removal. Metal-organic frameworks (MOFs)-derived metal/carbon composites, surpassing the limitations of separate components, exhibit synergistic effects, rendering them tremendously promising for environmental remediation. This comprehensive review systematically summarizes MOFs-based materials' properties and their structure-property relationships tailored for phosphate adsorption, thereby enhancing specificity towards phosphate. Furthermore, it elucidates the primary mechanisms influencing phosphate adsorption by MOFs-based composites. Additionally, the review introduces strategies for designing and synthesizing efficacious phosphorus capture and regeneration materials. Lastly, it discusses and illuminates future research challenges and prospects in this field. This summary provides novel insights for future research on superlative MOFs-based adsorbents for phosphate removal.

Bimetallic PCN-333 with Modulated Crystallization and a Porosity Structure for a Highly Efficient Removal of Congo Red

Bimetallic metal-organic frameworks (BMOFs) have garnered significant attention in the field of environmental remediation due to their more diverse adsorption sites compared to monometallic metal-organic frameworks (MOFs). Different energy barriers must be overcome for different metal ions and organic linkers to form MOFs. However, the impact of the synthesis temperature on the crystallization and porosity structure of BMOFs has been rarely studied. In this work, PCN-333 series-based BMOFs with different Fe/Al ratios were prepared by a solvothermal method at temperatures of both 135 and 150 °C. The synthesis temperature and Fe/Al ratio have significant effects on the crystal structure and specific surface area of bimetallic PCN-333, leading to the different adsorption performance of the PCN-333 for Congo red (CR). The Fe/Al-PCN-333-135(3:1) and Fe-PCN-333-150 exhibited the maximum CR adsorption capacities of 3233 and 3933 mg/g, respectively, surpassing the capacities of most previously documented adsorbents. The Langmuir model and pseudo-second-order kinetics can well describe the adsorption process of CR on Fe/Al-PCN-333-135(3:1) and Fe-PCN-333-150. Combining the isotherm adsorption behavior with the thermodynamic parameters, CR adsorption on BMOFs is a single-layer endothermic chemical adsorption. Furthermore, Fe/Al-PCN-333-135(3:1) and Fe-PCN-333-150 exhibited regenerability and reusability for three cycles with reasonable efficiency. This work is of great significance in the field of engineering BMOF materials to treat dye wastewater.

Bimetal doped Cu-Fe-ZIF-8/g-C3N4 nanocomposites for the adsorption of tetracycline hydrochloride from water

Bimetal doped Cu-Fe-zeolitic imidazole framework-8 (ZIF-8)/graphitic carbon nitride (GCN) (Cu-Fe-ZIF-8/GCN) nanocomposites were prepared via one-pot and ion-exchange methods. The main influencing factors, such as adsorbent concentration, TC concentration, initial pH, and coexisting ions, were evaluated in detail. Due to the suitable pore structures and the presence of multiple interactions on the surface, the nanocomposite showed a high adsorption capacity up to 932 mg g-1 for tetracycline hydrochloride (TC), outperforming ZIF-8 by 4.8 times. The adsorption kinetics and adsorption isotherm were depicted in good detail using pseudo-second-order kinetic and Langmuir models, respectively. Thermodynamic calculation revealed that the adsorption of the nanocomposite under experimental conditions was a spontaneous heat absorption process, and was primarily driven by chemisorption. After four cycles of use, the nanocomposite retained 87.2% of its initial adsorption capacity, confirming its high reusability and broad application prospects in removing tetracycline-type pollutants from wastewater.

Efficient extraction based on a polydimethylsiloxane/bimetallic ZnCo-MOF carbonization sponge coupled with GC-MS for the rapid analysis of volatile compounds in cumin

A novel porous polydimethylsiloxane/bimetallic ZnCo-MOF carbonization (PDMS/ZnCo-MOF@C) sponge was successfully fabricated, followed by its utilization in GC-MS for the high efficiency extraction and determination of volatile compounds in cumin. The PDMS/ZnCo-MOF@C sponge exhibits outstanding properties with a considerable adsorption capacity, high surface area, and large pore volume and has shown potential as an ideal adsorbent for the separation and preconcentration of trace volatile compounds. The effect of different parameters on the extraction efficiency were investigated. Excellent analytical performances were achieved for the representative compounds (β-pinene, p-cymene, γ-terpinene, cuminaldehyde, and linalyl acetate), including wide linearity (2.31-440.1 ng) with high correlation coefficients (R2 ≥ 0.9979), low LODs (1.02-3.11 ng) and LOQs (2.45-7.08 ng), and satisfactory precision (intra-day RSDs ≤ 2.89% and inter-day RSDs ≤ 4.14%). The optimal method was applied for the analysis of cumin from different regions and 44 volatile compounds were identified. The correlation between the different regions of cumin and volatile compounds was explored using multivariate statistical analysis. These results demonstrated that PDMS/ZnCo-MOF@C is an efficient, simple and sensitive material for use in the pretreatment technique for the determination of the volatile compounds in aromatic plants.

Adsorption of tetracycline from aqueous solution by ZIF-8: Isotherms, kinetics and thermodynamics

In this study, ZIF-8 nanoparticles were synthesized using a simple method at room temperature. The ZIF-8 nanoparticles were then characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET (Brunauer-Emmett-Teller) specific surface area, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and zeta potential. Subsequent batch adsorption experiments evaluated the adsorption performance of ZIF-8 on tetracycline, examining key pa-rameters like reaction time, pH, temperature, and adsorbent dosage. The results revealed a removal rate for TC of up to 90.59%. The adsorption data aligned with the Sips model, showcasing a maximum adsorption capacity of 359.61 mg/g at 303K. Further, the adsorption kinetics adhered to the pseudo-second-order kinetic model with an equilibrium adsorption capacity of 90 mg/g at 303K. The considerable specific surface area of ZIF-8, standing at 1674.169 m2/g, likely enhances the adsorption efficacy. Analysis using XRD and FTIR confirmed the adsorption of TC on the ma-terial's surface. Overall, the predominant driving forces behind the adsorption process were identified as electrostatic interactions and π-π stacking interactions.

Heterogeneous MIL-88A on MIL-88B hybrid: A promising eco-friendly hybrid from green synthesis to dual application (Adsorption and photocatalysis) in tetracycline and dyes removal

Herein, the green synthesis of heterogeneous dual functional MIL88A-on-MIL88B hybrids (MIL: Materials InstituteLavoisier) with different amounts of MIL88B compared to MIL88A, including 1:2, 1:1, and 2:1, has been carried out. The photocatalytic degradation of tetracycline and adsorption of tetracycline and dyes (Direct Red 80, Direct Red 23, Acid Blue 92, and Reactive Orange 14) were investigated. Although the ratio of MIL88A-on-MIL88B (1:1) hybrid displayed the best activity, there is a slight difference in the photocatalytic performance of the other mass ratios studied. The result revealed that after 70 min of forming MIL88A on MIL88B, the best pollutant removal performance is obtained. During the limited synthesis time, the lopsided growth of MIL88A on the MIL88B surface limits the formation of sufficient functional groups and new pores between MIL88B as the substrate and MIL88A, which are effective and decisive in the performance. In the photocatalytic studies, the synthesized composite had good compatibility with the zero-order kinetics, and hydroxyl radicals were recognized as the most active species in the photocatalytic reaction. In the adsorption process, the MIL88A-on-MIL88A composite followed pseudo-second-order kinetics and the Langmuir isotherm. Besides, mechanisms such as π-π interaction/stacking, hydrogen bonding, and π-metal interaction were proposed for the pollutant adsorption process.

Tailoring the topology of ZIF-67 metal-organic frameworks (MOFs) adsorbents to capture humic acids

Chlorination is a versatile technique to combat water-borne pathogens. Over the last years, there has been continued research interest to abate the formation of chlorinated disinfection by-products (DBPs). To prevent hazardous DBPs in drinking water, it is decided to diminish organic precursors, among which humic acids (HA) resulting from the decomposition and transformation of biomass. Metal-organic frameworks (MOFs) such as zeolitic imidazolate frameworks (ZIFs) have recently received tremendous attention in water purification. Herein, customized ZIF-67 MOFs possessing various physicochemical properties were prepared by changing the cobalt source. The HA removal by ZIF-67-Cl, ZIF-67-OAc, ZIF-67-NO3, and ZIF-67-SO4 were 85.6%, 68.9%, 86.1%, and 87.4%, respectively, evidently affected by the specific surface area. HA uptake by ZIF-67-SO4 indicated a removal efficiency beyond 90% in 4  90% after 60 min mixing the solution with 0.3 g L-1 ZIF-67-SO4. Notably, an acceptable removal performance (∼72.3%) was obtained even at HA concentrations up to 100 mg L-1. The equilibrium data fitted well with the isotherm models in the order of Langmuir> Hill > BET> Khan > Redlich-Peterson> Jovanovic> Freundlich > and Temkin. The maximum adsorption capacity qm for HA uptake by ZIF-67-SO4 was 175.89 mg g-1, well above the majority of adsorbents. The pseudo-first-order model described the rate of HA adsorption by time. In conclusion, ZIF-67-SO4 presented promising adsorptive properties against HA. Further studies would be needed to minimize cobalt leaching from the ZIF-67-SO4 structure and improve its reusability safely, to ensure its effectiveness and the economy of adsorption system.

Effective adsorption of bisphenol A from aqueous solution using phosphoric acid-assisted hydrochar

Sycamore leaf biochar (PSAC) was prepared by a two-step phosphoric acid-assisted hydrothermal carbonization combined with a short-time activation method. The characterization results showed that the introduction of phosphoric acid molecules and thermal activation resulted in a substantial increase in the specific surface area (994.21 m2/g) and microporous capacity (0.307 cm3/g) of PSAC. The batch adsorption results showed that the adsorption process of PSAC on bisphenol A (BPA) was best described by the pseudo-second-order kinetic model and Sips isothermal model, with a maximum adsorption capacity of 247.42 mg/g. The adsorption of BPA onto PSAC was determined to be a spontaneous endothermic process. The equilibrium adsorption capacity of PSAC exhibited an upward trend with increasing initial BPA concentration and temperature while decreasing with higher adsorbent dosage and pH value. Coexisting cations and humic acids in water have little impact on the adsorption performance of PSAC for BPA. The adsorption mechanism of BPA by PSAC was mainly governed by pore filling and hydrogen bonding interactions, π-π interactions, and intraparticle diffusion. Furthermore, PSAC demonstrated good reusability by its sustained adsorption capacity of BPA, which remained at 82.6% of the initial adsorption capacity even after four adsorption-desorption cycles. These findings highlight the potential of utilizing low-cost sycamore leaf biochar as an effective adsorbent for the removal of the endocrine disruptor BPA.

Bimetallic capture sites on porous La/Bi hydroxyl double salts for efficient phosphate adsorption: Multiple active centers and excellent selective properties

The rapid development of modern agriculture aggravated water eutrophication. Therein, efficient and selective removal of phosphorus in water is the key to alleviating eutrophication. It is well known that lanthanum (La)-based material is a kind of outstanding phosphorus-locking agent. Therefore, improving the property of La-based adsorbents is a hot topic in this field. Herein, novel porous hydroxyl double salts (La/Bi-HDS) with bimetallic capture sites were prepared. The experimental result shows that La/Bi-HDS could maintain the high removal rate in the solution with a higher concentration of competing ions and the maximum P adsorption quantity of La/Bi-HDS attains 168.12 mg/g. Mechanistic studies supported by density functional theory (DFT) calculation demonstrate that introducing Bi3+ optimizes the electronic structure of La, reducing adsorption energy. In addition, the surface analysis shows that the introduction of Bi, which increases the pore size and volume of the material, improves the utilization efficiency of the active site. In a word, the introduction of Bi element as a strategy of killing two birds with one stone successfully improved the performance of La-based adsorbent. It provided a new direction for developing an efficient phosphorus-locking agent.

Characterization of an Iron-Copper Bimetallic Metal-Organic Framework for Adsorption of Methyl Orange in Aqueous Solution

Iron-based organic frame material MIL-53 (Fe) was synthesized by the hydrothermal method with Cu2+ incorporated to obtain bimetallic composite MIL-53 (Fe, Cu). The structure and morphology of the material were characterized by SEM, XRD, BET, FTIR, XPS, and zeta potential. The adsorption performance of MIL-53 (Fe, Cu) on methyl orange was tested under a variety of conditions, including the effects of pH and material dosage, by the static adsorption test. The results show that under the condition of pH = 7, a temperature of 30°C, and an adsorbent dosage of 20 mg, the removal rate of MIL-53 (Fe, Cu) for methyl orange can reach more than 96% within 4 h, and the maximum adsorption capacity after fitting by the thermodynamic model can reach 294.43 mg/g, showing the excellent adsorption performance of MIL-53 (Fe, Cu) on methyl orange. In addition, by exploring the adsorption mechanism of MIL-53 (Fe, Cu) on methyl orange, it is found that the adsorption of MIL-53 (Fe, Cu) on methyl orange depends on chemical adsorption, as evidenced by combining Fe3+ and Cu2+ in the material with methyl orange molecules to form complexes to achieve adsorption. While the specific surface area of the material had no obvious effect on adsorption, the effects of pH, temperature, and concentration were explored. At a pH of 6.5, greater adsorption occurred at higher temperatures, as determined by thermodynamic model fitting, as well as with higher initial methyl orange molecule concentration.

Activated carbon modified titanium dioxide/bismuth trioxide adsorbent: One-pot synthesis, high removal efficiency of organic pollutants, and good recyclability

Considerable endeavors have focused on tightly combining adsorption with photocatalysis in designing composite materials for environmental pollution treatment. Recent advances in coupling titanium dioxide/bismuth trioxide (TiO₂/Bi₂O₃) with activated carbon (AC) show significantly enhanced photocatalytic performance but face critical limitations including low adsorption capacity and multi-step synthesis. In this work, we introduce a one-pot synthesis of activated carbon modified TiO₂/Bi₂O₃ composite materials (TiO₂/Bi₂O₃/AC). Thanks to the integrated adsorbent/photocatalyst system, TiO₂/Bi₂O₃/AC shows a drastically enhanced removal efficiency for sulfamethazine (>81%), far beyond the corresponding value of the reported AC/TiO₂/Bi₂O₃ adsorbent (<40%). Notably, the removal rates of other typical pollutants including tetracyclines, methyl orange, and rhodamine B are as high as >98%. Furthermore, TiO₂/Bi₂O₃/AC obtains >80% of its adsorption rate for the fifth cycle after simple photo-regeneration without any other post-treatments. Kinetic analysis and photoelectric characterization are carried out to provide insight into adsorption mechanism. Therefore, this work demonstrates a considerable potential to design and construct other multifunctional adsorbents with advanced performance.

SiC@FeZnZiF as a Bifunctional Catalyst with Catalytic Activating PMS and Photoreducing Carbon Dioxide

Herein, we encapsulated modified silicon carbide nanoparticles utilizing a metal-organic backbone. E-SiC-FeZnZIF composites were successfully prepared via Fe doping. The catalysis activity of this bifunctional composite material was evaluated by the degradation of tetracycline (THC) and carbamazepine (CBZ) and the reduction of carbon dioxide (CO₂). Nano SiC has received widespread attention in advanced oxidation applications, especially in the catalytic activation of peroxymonosulfate (PMS). However, the inferior activity of SiC has severely restricted its practical use. In this study of dual functional composite materials, nano SiC was firstly etched under aqueous alkali. Then, zeolite imidazolate frame-8 (ZIF-8) was used for immobilization. The filling of the etched nano SiC with FeZnZiF was confirmed by SEM, XRD, FTIR, BET, and XPS analyses. In addition, E-SiC-FeZnZIF exhibited excellent catalytic activation of peroxymonosulfate (PMS) to oxidize water pollutants, which can degrade tetracycline hydrochloride (THC), achieving a removal rate of 72% within 60 min. Moreover, E-SiC-FeZnZIF exhibited a relatively high CO₂ reduction rate with H₂O. The yields of CO and CH₄ were 0.085 and 0.509 μmol g^-1, respectively, after 2 h, which are higher than that of 50 nm of commercial SiC (CO: 0.084 μmol g^-1; CH₄: 0.209 μmol g^-1). This work provides a relatively convenient synthesis path for constructing metal skeleton composites for advanced oxidation and photocatalytic applications. This will have practical significance in protecting water bodies and reducing CO₂, which are vital not only for maintaining the natural ecological balance and negative feedback regulation, but also for creating a new application carrier based on nano silicon carbide.

Facile synthesis of ZIF-8-lignosulfonate microspheres with ultra-high adsorption capacity for Congo red and tetracycline removal from water

Zeolitic imidazolate frameworks (ZIFs) can be used as adsorbent to efficiently adsorb organic pollutants. However, the hydrophobicity of the ZIFs may be easily to form ZIFs nanoparticles aggregates, hampering the effective and practical application in adsorption. In this study, novel spherical composites of ZIF-8 incorporated with lignosulfonate (LS) were synthesized by in-situ growth method. The effects of different mass ratios of LS and Zn in ZIF-8-LS composites were evaluated with respect to structural characteristics and adsorption properties. As an adsorbent for adsorptive removing Congo Red (CR) and tetracycline (TC) from water, the prepared ZIF-8-LS₄ shows the best adsorption capacity of 31.5 mg g^-1 and 48 mg g^-1, respectively. The spherical structure facilitates the contact between the ZIF-8 and the adsorbed substance, in addition to the H-bonding, electrostatic and π-π stacking interactions also contribute to the improvement of the adsorption performance of the ZIF-8-LS₄ composite. The outstanding adsorption capacity and good reusability of the ZIF-8-LS₄ composite provide a good prospect for the effective removal of other contaminants from water.

Fe3O4/ZIFs-based magnetic solid-phase extraction for the effective extraction of two precursors with diverse structures in aflatoxin B1 biosynthetic pathway

The aflatoxin B₁ (AFB₁) early warning technique based on precursors is an effective strategy for the prevention of AFB₁ contamination risk. The determination of precursors is imperative to ensure the efficiency of the early warning technique. Herein, a controllable magnetic adsorbent Fe₃O₄/ZIFs was first introduced for the effective extraction and determination of averantin (AVN) and sterigmatocystin (ST) precursors in cereal by combining magnetic solid-phase extraction (MSPE) and high-performance liquid chromatography (HPLC). Benefiting from the abundant adsorption sites and multifunctional groups matching the analytes, Fe₃O₄/ZIFs effectively and simultaneously extracted AVN and ST with great differences in polarity and structure via multiple interactions. AVN was extracted by Fe₃O₄/ZIFs mainly through π-π and hydrophobic interactions, while ST was extracted predominantly by electrostatic interactions and surface complexation. The limits of detection were 0.08 μg kg^-1 (AVN) and 0.36 μg kg^-1 (ST). The developed method exhibited satisfactory spiked recoveries (79.1%-105.4%) in the determination of AVN and ST in rice. This work provides a novel analytical strategy for further studying AFB₁ early warning technique and the formation and transformation of aflatoxins.

Pyrolysis temperature affects the physiochemical characteristics of lanthanum-modified biochar derived from orange peels: Insights into the mechanisms of tetracycline adsorption by spectroscopic analysis and theoretical calculations

Biochar (BC) derived from orange peels was modified using LaCl₃ to enhance its tetracycline (TC) adsorption capacity. SEM-EDS, FT-IR, XRD, and BET were used to characterize the physiochemical characteristics of La-modified biochar (La-BC). Batch experiments were conducted to investigate the effects of several variables like pyrolysis temperature, adsorbent dosage, initial pH, and coexisting ions on the adsorption of TC by La-BC. XPS and density functional theory (DFT) were used to elucidate the TC adsorption mechanism of La-BC. The results demonstrated that La was uniformly coated on the surface of the La-BC. The physiochemical characteristics of La-BC highly depended on pyrolysis temperature. Higher temperature increased the specific surface area and functional groups of La-BC, thus enhancing its TC adsorption capacity. La-BC prepared at 700 °C (BC@La-700) achieved the maximum adsorption capacity of 143.20 mg/g, which was 6.8 and 4.6 times higher than that of BC@La-500 and BC@La-600, respectively. The mechanisms of TC adsorption by La-BC were most accurately described by the pseudo-second-order kinetic model. Furthermore, the adsorption isotherm of La-BC was consistent with the Freundlich model. BC@La-700 achieved good TC adsorption efficiencies even at a wide pH range (pH 4-10). Humic acid significantly inhibited TC adsorption by La-BC. The presence of coexisting ions (NH₄⁺, Ca²⁺, NO₃^-) did not significantly affect the adsorption capacity of La-BC, particularly BC@La-700. Moreover, BC@La-700 also exhibited the best recycling performance, which achieved relative high adsorption capacity even after 5 cycles. The XPS results showed that π-π bonds, oxygen-containing functional groups, and La played a major role in the adsorption of TC on La-BC. The result of DFT showed that the adsorption energy of La-BC was the greatest than that of other functional groups on biochar. Collectively, our findings provide a theoretical basis for the development of La-BC based materials to remove TC from wastewater.

Synthesis and characterization of zeolitic imidazolate frameworks nanocrystals and their application in adsorption and detoxification of gossypol in cottonseed oil

Three zeolitic imidazolate frameworks (ZIFs) materials including ZIF-8 (H₂O), ZIF-8 (methanol) and ZIF-L were synthesized and applied to the adsorption and detoxification of gossypol in cottonseed oil. The characterization results showed three ZIFs materials had good crystal structure, thermal stability and high specific surface area. The ZIFs materials had also good adsorption performance for gossypol and their adsorption processes can be described by the pseudo-second-order adsorption kinetic models. Adsorption isotherm analysis indicated that Langmuir model expressed a better conformity than Freundlich model, suggesting that the adsorption was the single-layer adsorption on a uniform site. Furthermore, the spiked experiment showed that the detoxification rate of ZIFs materials in vegetable oil was 72-86 %. A satisfied detoxification rate of 50-70 % was found in the detoxification experiment of real cottonseed oil samples. Therefore, these results demonstrate the great potential of using ZIFs materials as detoxification in cottonseed oil.

Bimetallic MOFs loaded cellulose as an environment friendly bioadsorbent for highly efficient tetracycline removal

Due to the increasingly serious antibiotic-related pollution, it is crucial to develop novel green bioadsorbents to effectively remove antibiotics from aqueous solutions. In this study, Fe doped zeolitic imidazolate frameworks-8 loaded cellulose (Fe/ZIF-8@cellulose) aerogels were prepared. The synthesized Fe/ZIF-8@cellulose aerogels were characterized experimentally including morphology observation and chemical compositions determination. The effects of bioadsorbent dosage, solution pH, adsorption time, initial TC concentration and adsorption temperature on the TC adsorption behaviors were systematically studied. Due to the introduction of Fe in the ZIF-8, the maximum adsorption capacity of Fe/ZIF-8@cellulose for TC could reach as high as 1359.2 mg/g, which is higher than the reported ZIF-8 loaded polysaccharide based adsorbents. The adsorption kinetics and isotherm of TC adsorption were also determined. With the cellulose as the matrix to load Fe/ZIF-8, the obtained Fe/ZIF-8@cellulose aerogels exhibited good reusability. Most importantly, the TC adsorption mechanism was proposed. The results of our finding suggest that the Fe doping into MOFs is an effective strategy to improve the antibiotics adsorption performance and the application of cellulose as the matrix is a valuable method to increase the cyclic utilization. This study highlights the potentials of applying the Fe/ZIF-8@cellulose aerogels in the antibiotics removal for practical wastewater.

Adsorption performance and optimization by response surface methodology on tetracycline using Fe-doped ZIF-8-loaded multi-walled carbon nanotubes

Herein, an iron-doped ZIF-8-loaded multi-walled carbon nanotube (FZM) was synthesized and its adsorption performance on tetracycline (TC) was investigated. The experimental conditions (solution pH, temperature, adsorbent dose) were optimized by Box-Behnken design (BBD) in response surface methodology (RSM). The results show that the adsorption effect of TC by FZM is optimal under the conditions of temperature = 298 K, pH = 6, and contact time = 360 min. The adsorption processes of TC by FZM follow the pseudo-second-order (PSO) kinetic and Freundlich isotherm models, indicating that chemisorption is the dominant factor and the adsorption reaction is multi-layer, with a theoretical maximum saturation capacity of 1111.11 mg/g at 298 K. The adsorption thermodynamic results indicate that the adsorption of TC by FZM is a spontaneous and endothermic process. The mechanism of TC adsorption by FZM possibly occurs through hydrogen bonding, surface complexation, π-π interaction, and electrostatic interaction. From the statistical results, the optimal adsorption capacity of TC by FZM is 599.78 mg/g at a pH of 7.1, a temperature of 312.5 K, and an adsorbent dose of 64.43 mg/L, with a deviation of 1.73% from the actual value. Furthermore, regeneration experiments demonstrate that FZM has excellent reusability with a 15% loss of adsorption capacity after four cycles. This study provides some insights to study the adsorption behavior of TC by MOFs and the optimization of the adsorption experimental conditions, and also shows the potential of FZM for TC removal.

Polydopamine-mediated modification of ZIF-8 onto magnetic nanoparticles for enhanced tetracycline adsorption from wastewater

Magnetic nanoparticle materials which could be used to remove tetracycline were confined seriously due to their poor stability and unsatisfactory reusability. Here, we facilely prepared novel zeolitic imidazolate framework-8 (ZIF-8) functionalized magnetic nanoparticles (Fe₃O₄@PDA-ZIF-8) adsorbent utilizing polydopamine as a bond to establish a connection between zeolitic imidazolate framework-8 and Fe₃O₄, which could improve the stability of magnetic nanoparticles and enhance the tetracycline adsorption capacity simultaneously. The prepared nanocomposites were characterized and their TC adsorption abilities under various experiment conditions (contact time, TC initial concentration and pH values) were also investigated. Experimental results proved that the prepared adsorbent showed superior TC adsorption capacities (92.01 mg/g at pH = 7). Further, the adsorption mechanisms were comprehensively studied and the prepared adsorbent showed satisfactory stability and reusability during the cycle experiment. Altogether, our findings provided a feasible way to design and construct functional magnetic MOF materials for enhancing tetracycline adsorption from wastewater.

ZIF-8 metal organic framework materials as a superb platform for the removal and photocatalytic degradation of organic pollutants: a review

Metal organic frameworks (MOFs) are attracting significant attention for applications including adsorption, chemical sensing, gas separation, photocatalysis, electrocatalysis and catalysis. In particular, zeolitic imidazolate framework 8 (ZIF-8), which is composed of zinc ions and imidazolate ligands, have been applied in different areas of catalysis due to its outstanding structural and textural properties. It possesses a highly porous structure and chemical and thermal stability under varying reaction conditions. When used alone in the reaction medium, the ZIF-8 particles tend to agglomerate, which inhibits their removal efficiency and selectivity. This results in their mediocre reusability and separation from aqueous conditions. Thus, to overcome these drawbacks, several well-designed ZIF-8 structures have emerged by forming composites and heterostructures and doping. This review focuses on the recent advances on the use of ZIF-8 structures (doping, composites, heterostructures, etc.) in the removal and photodegradation of persistent organic pollutants. We focus on the adsorption and photocatalysis of three main organic pollutants (methylene blue, rhodamine B, and malachite green). Finally, the key challenges, prospects and future directions are outlined to give insights into game-changing breakthroughs in this area.

Efficient peroxymonosulfate activation of immobilized Fe-N-C catalyst on ceramsite for the continuous flow removal of phenol

Nowadays, developing environmentally friendly catalysts with both low cost and high efficiency was still a challenge in actual organic wastewater purification. Herein, the Fe-N-C catalyst was successfully immobilized on solid waste derived ceramsite for efficient degradation of phenol under continuous flow conditions by activating peroxymonosulfate (PMS). After the introduction of ceramsite, the microstructure of Fe-N-C catalyst was changed from granular structure to worm-like structure, promoting the dispersion of the nanoscale catalyst and providing more reactive sites. Therefore, the phenol removal rate and mineralization rate of the obtained 0.5FNNC within 30 min were up to 96.79% and 71.79%, respectively. In addition, the degradation rate of the optimal composite (0.5FNNC)/PMS system was about 4.06 times higher than that of bare Fe-N-C/PMS system. Intriguingly, the Fe ion leaching from 0.5FNNC during the degradation reaction was significantly lower than bare Fe-N-C owing to the strong catalyst-support chemical bonding. Based on electron paramagnetic resonance, quenching experiments, X-ray photoelectron spectroscopy analysis and electrochemical analysis, it was indicated that the non-radical processes (¹O₂ and high valent iron-oxo species) should be responsible for the phenol degradation. Meanwhile, the possible phenol degradation pathways were proposed, and the intermediates were evaluated for ecotoxicity by ECOSAR. Finally, a preliminary economic analysis of this process was carried out. Overall, this work would provide a new strategy for the construction of ceramsite based multi-pore composite catalysts and the large-scale application of persulfate oxidation technology in organic wastewater treatment.

Efficient electro-catalyzed PMS activation on a Fe-ZIF-8 based BTNAs/Ti anode: An in-depth investigation on anodic catalytic behavior

Phenanthrene (PHE), mainly released from coal tar and petroleum distillation, is an important kind of prevalent polycyclic aromatic hydrocarbons (PAHs) contamination in China (up to 2.38 ± 0.02 mg/kg in soil and 8668 ng/L in surface water) and other countries in the world. Metal-organic frameworks (MOFs) show promising application prospects in the decontamination field, however, suffering from the intrinsic fragility and fine powder forms. Therefore, macroscopic MOFs architecture-sandwich-like Fe-ZIF-8/blue TiO₂ nanotube arrays (BTNAs)/Ti substrate (FBTT) anode with strong interfacial bonding (Fe-O-Ti and Fe-2-MIM-Ti coordination) was constructed using innovative in situ growth, condensation-crystallization-deposition, and pyrolysis methods, aiming at exploring the feasibility of MOFs-based anode/peroxymonosulfate (PMS) mediated PHE elimination, revealing the in-depth mechanisms, simultaneously overcoming the intrinsic drawbacks of MOFs. The FBTT-4 (doping content of 30 %) efficiently degraded PHE by 90.01 % and 74.5 % within 10 min at 350 μg/L and 3 mg/L, respectively, mediated by the ^·OH compared to the SO₄^·-, ¹O₂, and O₂^·-. Post-optimized range of anodic potential enabled (i) anodic oxidation, (ii) activation of water and PMS molecules to produce active species, (iii) capture of electrons in reactants to reduce Fe³⁺/Ti⁴⁺ to Fe²⁺/Ti³⁺, maintaining the proportion of Fe/Ti with low valence and thus stable PMS activation capacity, and (iv) regulation of the Fe/Ti d-band center to modulate the anode adsorption capacity. The further increment in anodic potential could promote "dark photocatalysis" with a Z-scheme-like mechanism. Thus, it is proposed that the development of macroscopic MOFs-based anode, especially those with small band gaps, represents vast potentials in electrocatalytic contamination elimination. Simultaneously, the MOFs-based anode is expected to fully exploit their catalytic capacities and solve their intrinsic defects as well.

Removal of Arsenic from Wastewater by Using Nano Fe3O4/Zinc Organic Frameworks

Efficient removal of arsenic in wastewater is of fundamental importance due to the increasingly severe arsenic pollution. In this study, a new composite adsorbent (Fe₃O₄@ZIF-8) for As(V) removal from wastewater was synthesized by encapsulating magnetic Fe₃O₄ nanoparticles into metal organic frameworks. In order to evaluate the feasibility of Fe₃O₄@ZIF-8 as an adsorbent for As(V) removal, the adsorption properties of Fe₃O₄@ZIF-8 were systematically explored by studying the effects of dosage, pH, adsorption isotherm, kinetics, and thermodynamics. Additionally, the characterization of Fe₃O₄@ZIF-8 before and after adsorption was analyzed thoroughly using various tests including SEM-EDS, XPS, BET, XRD, TG, FTIR, and the properties and arsenic removal mechanism of the Fe₃O₄@ZIF-8 were further studied. The results showed that the Fe₃O₄@ZIF-8 has a specific surface area of 316 m²/g and has excellent adsorption performance. At 25 °C, the initial concentration of arsenic was 46.916 mg/L, and pH 3 was the optimum condition for the Fe₃O₄@ZIF-8 to adsorb arsenic. When the dosage of the Fe₃O₄@ZIF-8 was 0.60 g/L, the adsorption of arsenic by the Fe₃O₄@ZIF-8 can reach 76 mg/g, and the removal rate can reach 97.20%. The adsorption process of arsenic to the Fe₃O₄@ZIF-8 can be well described by the Langmuir isotherm model and the second-order kinetic equation. At pH 3 and temperature 298 K, the maximum adsorption capacity of arsenic by the Fe₃O₄@ZIF-8 was 116.114 mg/g. Through the analysis of thermodynamic parameters, it is proved that the adsorption process of arsenic by the Fe₃O₄@ZIF-8 is a spontaneous endothermic reaction. The Fe₃O₄@ZIF-8 has broad prospects for removing As(V) pollution in wastewater, because of its strong adsorption capacity, good water stability, and easy preparation.

Preparation of Ag3PO4/CoWO4 S-scheme heterojunction and study on sonocatalytic degradation of tetracycline

In this study, 0.6Ag3PO4/CoWO4 composites were synthesized by hydrothermal method. The prepared materials were systematically characterized by techniques of scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption/desorption, and UV-vis diffuse reflectance spectrum (DRS). Furthermore, the sonocatalytic degradation performance of 0.6Ag3PO4/CoWO4 composites towards tetracycline (TC) was investigated under ultrasonic radiation. The results showed that, combined with potassium persulfate (K2S2O8), the 0.6Ag3PO4/CoWO4 composites achieved a high sonocatalytic degradation efficiency of 97.89 % within 10 min, which was much better than bare Ag3PO4 or CoWO4. By measuring the electrochemical properties, it was proposed that the degradation mechanism of 0.6Ag3PO4/CoWO4 is the formation of S-scheme heterojunction, which increases the separation efficiency of electron-hole pairs (e--h+) and generates more electrons and holes, thereby enhancing the degradation activity. The scavenger experiments confirmed that hole (h+) was the primary active substance in degrading TC, and free radicals (OH) and superoxide anion radical (O2-) were auxiliary active substances. The results indicated that 0.6Ag3PO4/CoWO4 nanocomposites could be used as an efficient and reliable sonocatalyst for wastewater treatment.